An existing regulator amplifier circuit includes a differential circuit to cause an output voltage to be coincident with a reference voltage.
In the regulator amplifier circuit, feedback is applied to the differential circuit to control a gate voltage of an output transistor according to a load current flowing through a load circuit, in order to output a fixed output voltage to an output terminal independent of the load current.
The regulator amplifier circuit preferably quickly responds (has high slew rate) to steep variation of the load current; however, it is necessary to cause a large amount of current to constantly flow through the differential circuit in order to obtain quick response in a case where a gate capacitance of the output transistor is large.